There are a wide variety of applications where heated or cooled fluid is delivered over a length of conduit Typical industrial applications include fluid coatings or adhesives that are applied at specific assembly or processing stations in a plant. The fluid may be stored in an area remote from the one or more dispensing stations. However, it is often advantageous to control the temperature of the fluid, whether to lower the viscosity to facilitate fluid transfer or to maintain a desired temperature at the point of application, as a matter of application process efficiency. It is generally preferred to perform the bulk temperature control at the point of introducing the fluid into the system, particularly where there are multiple application points. During delivery of the fluid to the application station, a change in fluid temperature will result if the ambient temperature varies from the initial control temperature. The temperature gradient increases as the difference between the ambient temperature and control temperature increases, and as the length of the conduit increases.
Other fluid delivery systems require the routing of fluid conduits carrying ambient temperature fluids through relatively cold or hot environments. For example, pipes carrying room temperature water through an outside environment may freeze up if the ambient temperature drops significantly below the freezing point of water. The pipes must then be heated, melting internal ice to restore flow until the ambient temperatures rise sufficiently. It is well known to insulate such pipes with a variety of insulating wraps or foams, however, in severe conditions such measures are often insufficient to prevent freezing of the liquid passing through the pipe.
Accordingly, in many fluid delivery systems it is desirable to actively reduce temperature variation along the conduit or even adjust the temperature along the conduit. U.S. Pat. No. 5,363,907 to Dunning et al. shows an example of one such system, whereby installation of a heat exchanger to an existing system without disassembly is possible. This design represents a substantial improvement over many earlier methods which required cutting, welding, or similar processes to install a coaxial heat exchanging system. Unless installed at the time of system construction, prior methods required separating the pipe to be heated, draining and purging the pipe, then sliding a larger section of pipe over the subject pipe. The exterior pipe could be used to circulate fluid past the interior pipe in a coaxial relationship. Once this was done, however, both the exterior pipe and the internal, subject pipe had to be welded or otherwise sealed, a time-intensive, potentially dangerous and costly prospect. The multiple sealing points further presented an added risk of leaks (in either the heated system or the exterior heating pipe) that can foul or damage the system and require downtime for maintenance. Because water is typically used as the heating fluid, corrosion tends to cause leaks whereby material can pass into the water stream or water can pass into the material in the inner pipe, having dire consequences.
For example, in systems where hot urethane material is transferred through a pipe, the accidental introduction of even a small quantity of water can cause solidification of the material within the entire system, ruining much of the equipment. Furthermore, many such systems utilize flammable, caustic or otherwise dangerous materials in their operation, often creating significant disposal and safety issues. Moreover, the systems must often be cleaned with toxic or flammable materials to prepare the system for reintroduction of fluid material.
In light of the above concerns, it is desirable to reduce material usage and labor. Further, obviating the need to drain and cut into an existing system would provide a significant improvement in safety.